The really bizarre thing about this thread is that a majority of responders are Level 3 and 4 Biotest customers. Chances are, you've taken in plenty of artificial sweeteners from the Surge, MD, Spike Shooters, Spike pills (they contain sorbitol) and other products. This is food for thought.
Regarding the "bigger appetite" that the OP mentioned, WTF? Drinking carbonated water makes people feel full, not emptier.
People do decide, "I'm being good by drinking this Diet Coke, so I'll have [insert junk food item.]" That's not an intrinsic flaw of Diet Coke, though, that's just the foolishness of the individual consumer. So, as can be said for pretty much anything, Diet Coke can be misused, in the wrong hands.